Geological differentiation of groundwater threshold concentrations of arsenic, vanadium and fluorine in El Bajio Guanajuatense, Mexico

Abstract

Groundwater background values, (GBV), of risky elements can be integrated as a component in groundwater management policies. Variations of GBV in rural areas with agricultural activity and in urban areas with industrial development can be related to contamination processes. Methods to calculate GBV were applied in Salamanca and Juventino Rosas, an industrial city and a farming community located in Central Mexico. A statistical treatment for rejection of deviant values was used for outliers (Dixon's Q test). GBV were calculated using the Grubb test. Variations in arsenic and vanadium GBV are explained in terms of potential contamination sources and migration mechanisms. Arsenic and vanadium are contained in particulate emitted by a thermoelectric plant. Particulate was deposited over vulnerable areas that facilitate its migration to local aquifers. Differences in fluoride GBV are explained in terms of the geological framework.